Blade member of cermet having surface reaction layer and process for producing same

ABSTRACT

A blade member for cutting tools comprises a cermet substrate having on a surface thereof a reaction layer. The reaction layer is composed of carbo-nitride of at least two metals in groups IV A , V A  and VI A , the metals including Ti. The reaction layer may be composed of oxy-carbo-nitride of the above metals. The reaction layer may consist of inner and outer layers, the inner layer being composed of carbo-nitride of the above metals while the outer layer is composed of oxy-carbo-nitride of the above metals. The blade members with the reaction layer exhibits excellent toughness, wear resistance and thermoplastic deformation resistance. There is also disclosed a process for producing the above blade member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a blade member or insert of cermet for cutting tools having a wear-resistant and thermoplastic deformation-resistant reaction layer on a surface thereof, the blade member being suited for high speed cutting.

2. Prior Art

Conventionally, cermets, containing as hard phase-constituting components a major proportion of titanium carbide (TiC) and/or titanium nitride (TiN), have been extensively used to form blade members or inserts for high speed cutting tools such as a turning tool, since such hard cermets are superior in wear-resistance to cemented tungsten carbide. However, such cermet blade members have not met the requirement of very high speed cutting operation of above 200 m/minute. Therefore, in order to meet this requirement, hard ceramics containing a major proportion of aluminum oxide (Al₂ O₃) have been proposed to form a blade member capable of very high speed cutting. However, such ceramics contain no binder and therefore are inferior in toughness. As a result, the use of such ceramics blade members has been limited to high speed finish cutting.

There has also been proposed and extensively used a high speed-cutting blade member made of cemented tungsten carbide and having on its surface a composite coating layer or layers composed of at least one material selected from the group consisting of TiC, TiN, titanium oxide (TiOx) and Al₂ O₃. Such coating layers are usually formed by a chemical vapor deposition process using reaction gas such as titanium tetrachloride, methane gas, hydrogen gas and nitrogen gas. Therefore, a deposition apparatus for forming such coating is large in size, and manufacturing costs of such surface-coated blade member are also increased. Further, the constituent parts of the deposition apparatus are susceptible to corrosion due to hydrochloric acid produced by chlorine gas generated upon decomposition of titanium tetrachloride. In addition, means for preventing leakage of such hydrochloric acid should be provided from a viewpoint of safety. Further, when the coating is formed on the blade member of cemented tungsten carbide by means of the chemical vapor deposition process, a decarburized η phase is inevitably formed in its substrate immediately below the deposited coating. The presence of such a decarburized phase will lower the toughness of the blade member so that the blade member will not always have a satisfactory cutting performance.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a blade member of cermet having on its surface a reaction layer which exhibits excellent wear resistance and thermoplastic deformation resistance, whereby the blade member exhibits excellent cutting performance particularly when a high speed cutting operation is carried out.

Another object is to provide a process for producing such a blade member.

According to the present invention, there is provided a blade member for cutting tools which comprises a substrate of cermet containing, apart from impurities, 10 to 35% by volume of at least one binder metal selected from the group consisting of Fe, Co, Ni, Cr, Mo, W and Al, 5 to 40% by volume of at least one compound selected from the group consisting of carbides and nitrides of metals in groups IV_(A), V_(A) and VI_(A) of the periodic table as hard phase-constituting components, and balance titanium carbide and titanium nitride as main hard phase-constituting components (volume ratio of titanium nitride to titanium carbide plus titanium nitride is 0.2 to 0.6), said substrate having on a surface thereof a reaction layer composed of carbo-nitride of at least two metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, said at least two metals including Ti, and said reaction layer having an average thickness of 0.5 to 15.0 μm.

According to a second aspect of the invention, a reaction layer on a cermet substrate of the above-mentioned components is composed of oxy-carbo-nitride of at least two metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, said at least two metals including Ti. This reaction layer has an average thickness of 0.5 to 10.0 μm.

According to a third aspect of the invention, a reaction layer on a cermet substrate of the above-mentioned components consists of inner and outer layers. The inner layer is composed of carbo-nitride of at least two metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, said at least two metals including Ti. The inner layer has an average thickness of 0.2 to 15.0 μm. The outer layer is composed of oxy-carbo-nitride of at least two metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, said at least two metals including Ti. The outer layer has an average thickness of 0.2 to 10.0 μm. The combined average thicknesses of the inner and outer layers is 0.5 to 20.0 μm.

The above-mentioned reaction layers on the cermet substrates exhibit excellent wear resistance and thermoplastic deformation resistance when a cutting operation is carried out at a high cutting speed of 150 to 250 m/min. using these blade members.

The starting materials of the cermet substrate are in the form of powder. These powder materials are mixed together and then compacted into a densified solid body. This densified solid body is sintered under vacuum of not more than 10⁻¹ torr to provide a cermet substrate. As a result, the cermet substrate has reduced nonmetallic content (mainly nitrogen content) due to denitridation during the sintering operation.

In the case where the reaction layer, composed of carbo-nitride of metals and having an average thickness of 0.5 to 15.0 μm, is formed in a surface of the cermet substrate, the cermet substrate is heated at temperatures of 1100° to 1300° C. in an atmosphere of N₂. The reaction layer so formed has a high hardness and a high strength of bonding to the substrate body because there exists no clear linear boundary between the reaction layer and the cermet substrate. Further, no decarburized η brittle phase is formed immediately below the reaction layer as is the case with the chemical deposited cemented carbide substrate. Further, the hard phase-constituting components react with N₂ during the heating operation and are finely dispersed uniformly in the surface of the substrate so that the toughness of the resultant blade member is not lowered at all. Therefore, this blade member having the above-mentioned reaction layer is excellent in wear resistance and toughness.

The reaction layer is formed through the reaction of the denitridated surface of the substrate with N₂ during the heating treatment. This reaction is represented by the following formula:

    (Ti, M)(CN).sub.1-a +(a/2)N.sub.2 →(Ti, M)(CN)

wherein M is at least one metal selected from the group consisting of metals in groups IV_(A), V_(A) and VI_(A) of the periodic table except for Ti, and a is the amount of denitridation. The reaction layer should preferrably has the following composition formula:

    (Ti, M) (CxNy)

wherein 0.05≦x≦0.4 and 0.6≦y≦0.95 are provided in terms of molar ratio.

In the reaction layer, concentrations of Ti and N become higher toward its surface, and concentrations of M and C become higher in a direction away from its surface. Thus, the reaction layer has continuous gradient of such concentration. And, the reaction layer has no free graphite or even if there exists any free graphite, the amount of free graphite is negligible since the surface of the substrate is denitridated during the sintering under vacuum of not more than 10⁻¹ torr. As described above, the reaction layer composed of carbo-nitride of metals has an average thickness of 0.5 to 15.0 μm. If the average thickness is less than 0.5 μm, the reaction layer does not possess desired wear resistance and thermoplastic deformation resistance. On the other hand, if the average thickness exceeds 15 μm, the resultant blade member has a reduced toughness.

In the case where the reaction layer, composed of oxy-carbo-nitride of metals and having an average thickness of 0.5 to 10.0 μm, is formed in a surface of the cermet substrate, the substrate is heated at temperatures of 1100° to 1300° C. either in an atmosphere of one or both of CO and CO₂ or in an atmosphere of N₂ and one or both of CO and CO₂.

This reaction layer is formed through the reaction of the denitridated surface of the substrate with either CO or CO plus N₂ (CO₂ reacts with C in a reaction chamber to form CO: CO₂ +C→2CO). The reaction layer composed of oxy-carbo-nitride of metals is formed either by the following reaction:

    (Ti, M)(CN).sub.1-1 +a(CO)→(Ti, M)(CNO)

wherein M is at least one metal selected from the group consisting of metals in groups IV_(A), V_(A) and VI_(A) of the periodic table except for Ti, and a is the amount of denitridation or by the following reaction:

    (Ti, M)(CN).sub.1-a' +(b'/2)N.sub.2 +c'(CO)→(Ti, M)(CNO)

wherein a' is the amount of denitridation (a'=b'+c'). The reaction layer should preferrably has the following composition formula:

    (Ti, M) (CxNyOz)

wherein x is 0.2 to 0.7, y is 0.1 to 0.7 and z is 0.05 to 0.4 (molar ratio). Although the rate of formation of this reaction layer composed of oxy-carbo-nitride of metals is lower than that of the reaction layer of carbo-nitride of metals, the former is higher in wear resistance than the latter if they have the same thickness. Further, the hard phase-constituting components react with CO during the heating operation and are finely dispersed uniformly in the surface of the substrate so that the toughness of the resultant blade member is not lowered at all. Therefore, this blade member having the above-mentioned reaction layer exhibits excellent wear resistance and toughness.

In this reaction layer, concentrations of Ti, C and O become higher toward its surface, and concentrations of M and N become higher in a direction away from its surface. Thus, the reaction layer has continuous gradient of such concentration.

As described above, the reaction layer composed of oxy-carbo-nitride of metals has an average thickness of 0.5 to 10.0 μm. If the average thickness is less than 0.5 μm, the reaction layer does not possess desired wear resistance and thermoplastic deformation resistance. On the other hand, if the average thickness exceeds 10 μm, the resultant blade member has a reduced toughness.

In the case where the reaction layer, consisting of the inner layer of carbo-nitride of metals and the outer layer of oxy-carbo-nitride of metals, is formed in a surface of the cermet substrate, a base reaction layer composed of carbo-nitride of metals is first formed according to the procedure described above for the reaction layer of carbo-nitride of metals. In this case, however, the base reaction layer has an average thickness of 0.5 to 20.0 μm. The inner portion of the base reaction layer serves as the above-mentioned inner layer. Then, if there exists no free carbon in the base reaction surface of the cermet substrate, the substrate is heated at 1100° to 1300° C. in an atmosphere of CO so that the outer layer of oxy-carbo-nitride of metals is formed in the surface of the base reaction surface. Alternatively, if there exists any free carbon in the base reaction layer, the substrate is heated at 1100° to 1300° C. either in an atmosphere of CO₂ or in an atmosphere of CO₂ and CO to form the outer layer of oxy-carbo-nitride of metals in the surface of the base reaction surface. In either case, as described above, the outer layer has an average thickness of 0.2 to 10.0 μm, and the inner layer of carbo-nitride of metals has an average thickness of 0.2 to 15.0 μm. But, the combined average thickness of the inner and outer layers should be 0.5 to 20.0 μm. If the average thickness of each of the inner and outer layers is less than 0.2 μm, and if their combined average thicknesses is less than 0.5 μm, the reaction layer composed of the inner and outer layers does not possess desired wear resistance and thermoplastic deformation resistance. On the other hand, if the average thicknesses of the outer and inner layers exceed 10.0 μm and 15.0 μm, respectively, and if their combined average thicknesses exceed 20.0 μm, the resultant blade member has a reduced toughness.

The provision of the inner layer composed of carbo-nitride of metals and the outer layer composed of oxy-carbo-nitride of metals serves to further enhance the wear resistance and thermoplastic deformation resistance of the overall reaction layer.

The content of the binder metal or metals in the cermet substrate is 10 to 35% by volume. The binder metal or metals serve to enhance the toughness of the cermet substrate, and if the content of the binder metal or metals is less than 10% by volume, a desired toughness of the cermet substrate is not achieved. On the other hand, if the content exceeds 35% by volume, wear resistance of the cermet substrate is lowered.

The carbides and nitrides of metals in group IV_(A), V_(A) and VI_(A) serve to improve plastic deformation resistance. Further, carbides of Mo and W serve to enhance the toughness of the cermet substrate. The content of the metal carbide and/or nitride is 5 to 40% by volume. If its content is less than 5% by volume, the desired effects can not be achieved. If the content exceeds 40% by volume, the wear resistance of the cermet substrate is lowered, and the reaction layer on the surface of the substrate fails to exhibit excellent wear resistance.

The balance titanium carbide and titanium nitride also serve as main hard phase-constituting components of the cermet substrate. The volume ratio of titanium nitride to titanium carbide plus titanium nitride should be 0.2 to 0.6. If the volume ratio is less than 0.2, the content of titanium nitride is correspondingly low so that the amount of denitridation of the substrate during the vacuum sintering operation is too small. As a result, a considerable amount of free carbon will exist in the resultant reaction surface layer formed through the subsequent heating treatment. This would adversely affect the wear resistance of the reaction layer and the toughness of the cermet substrate. On the other hand, if the volume ratio exceeds 0.6, the content of titanium nitride is correspondingly increased so that the amount of denitridation of the surface layer of the substrate during the vacuum sintering operation is too large. As a result, the resultant blade member has a roughened surface so that its accuracy is adversely affected. In addition, the wear resistance of the reaction surface and the toughness of the blade member are lowered.

The compacted body of the powder materials should be sintered under vacuum of not more than 10⁻¹ torr to form the cermet substrate. If the sintering is carried out under vacuum of more than 10⁻¹ torr, the nonmetallic content (mainly, the nitrogen content) of the cermet substrate is not sufficiently reduced. As a result, the reaction layer having desired properties can not be formed in the surface of the cermet substrate at the subsequent heating treatment.

The heat treatment of the cermet substrate is carried out at temperatures of 1100° to 1300° C. If the temperature is less than 1100° C., the speed of formation of the reaction layer is lowered and therefore the production rate of the blade member is low. On the other hand, if the temperature is more than 1300° C., the reaction surface is so roughened that accuracy of the blade member is adversely affected.

The impurities contained in this cermet substrate include O₂, B and Si. If the content of the impurities is less than 2% by volume, they will not affect the intended properties of the cermet substrate at all.

DESCRIPTION OF THE INVENTION

The invention will now be illustrated by the following Examples:

The following Examples 1 to 3 illustrates blade members having on a surface a reaction layer composed of carbo-nitride of metals.

EXAMPLE 1

Powders of TiC (average particle size: 1.5 μm), TiN (1.0 μm), TaC (1.0 μm), WC (1.2 μm), Mo (0.8 μm), Ni (2.5 μm) and Co (1.2 μm) were prepared as starting materials. The starting materials were mixed together in predetermined amounts to provide a mixture. Then, the mixture was compacted into a densified solid body. Then, the densified body was sintered at temperature of 1450° C. for 1.5 hours under vacuum of 10⁻² torr to form a cermet substrate. The cermet substrate consisted of 45% by volume TiC, 25% TiN, 5% TaC, 5% WC, 10% Mo, 4% Ni and 6% Co (the ratio of TiN to TiC plus TiN was 0.36). The cermet substrate was then ground into a shape conforming to JIS·SNP432. Cermet substrates prepared in this manner were subjected to heat treatment under conditions shown in Tabe 1 to produce blade members 1 to 7 of this invention. The composition of each reaction layer shown in Table 1 was that of the central portion of the reaction layer.

For comparison purposes, cermet substrates prepared according to the above procedure were subjected to heat treatment at temperatures above the upper temperature limit of this invention, i.e., 1300° C., to produce comparison blade members 1 and 2. Also, there were provided comparison blade member 3 of cermet containing TiC, Ni and Mo and WC-based comparison blade member 4 having on a surface 6 μm thick coating composed of a layer of TiC and layer of Al₂ O₃. The comparison blade members 3 and 4 were commercially available.

The blade members 1 to 7 of this invention and the comparison blade members 1 to 4 were each attached to a holder and subjected to a continuous cutting test to determine wear resistance. The conditions for this continuous cutting test were as follows:

Workpiece: a bar of steel (JIS·SNCM-8; AISI·4340; Hardness: HB240)

Cutting speed: 250 m/minute

Feed rate: 0.30 mm/revolution

Depth of cut: 1.5 mm

Time: 10 minutes

After this continuous cutting test, the flank wear and the crater wear of each blade member were observed. The results obtained are shown in Table 1.

Also, the blade members 1 to 7 of this invention and the comparison blade members 1 to 4 were subjected to an intermittent cutting test to determine toughness. In this intermittent test, two workpieces in the form of block were fixedly secured to a turning support member. A tool holder holding the blade member was located adjacent to the support member so that during the turning of the support member, the outer surfaces of the two workpieces were intermittently brought into cutting engagement with the blade member. In this test, it was determined how many blade members of the same construction out of ten were subjected to chipping. The conditions for this intermittent cutting test were as follows:

Workpiece: a block of steel (JIS·SNCM-8; Hardness: HB280)

Cutting speed: 140 m/minute

Feed rate: 0.3 mm/revolution

Depth of cut: 2 mm

Time: 3 minutes

The results of this intermittent cutting test are shown in Table 1.

                                      TABLE 1                                      __________________________________________________________________________                                                          Intermittent              Heat treatment                             Continuous cutting                                                                       cutting test                         Heat    Reaction layer          test      Number of chipped         Kind of                                                                              Pressure                                                                            tempera-                                                                               Composition of carbo-nitride of metals:                                                           Average                                                                             Flank                                                                               Crater                                                                              blade members/            blade of N.sub.2                                                                          ture Time                                                                              (Ti, M) (CxNy)     thickness                                                                           wear wear number of tested          member                                                                               (torr)                                                                              (°C.)                                                                        (h)                                                                               (molar ratio)      (μm)                                                                             (mm) (μm)                                                                             members                   __________________________________________________________________________     Blade                                                                          members of                                                                     this                                                                           invention                                                                      1     600  1240 10 (Ti.sub.0.80 Ta.sub.0.06 W.sub.0.03 Mo.sub.0.11)--(C.su                        b.0.18 N.sub.0.82) 3.5  0.19 25   1/10                      2     550  1250  8 (TI.sub.0.80 Ta.sub.0.06 W.sub.0.03 Mo.sub.0.11)--(C.su                        b.0.15 N.sub.0.83) 4.0  0.16 20   2/10                      3     500  1260  7 (Ti.sub.0.81 Ta.sub.0.06 W.sub.0.03 Mo.sub.0.10)--(C.su                        b.0.16 N.sub.0.84) 4.0  0.16 20   2/10                      4     450  1270  6 (Ti.sub.0.81 Ta.sub.0.06 W.sub.0.03 Mo.sub.0.10)--(C.su                        b.0.17 N.sub.0.83) 4.0  0.16 20   2/10                      5     400  1280  8 (Ti.sub.0.82 Ta.sub.0.05 W.sub.0.03 Mo.sub.0.10)--(C.su                        b.0.20 N.sub.0.80) 6.0  0.14 15   3/10                      6     450  1290 13 (Ti.sub.0.84 Ta.sub.0.05 W.sub.0.02 Mo.sub.0.09)--(C.su                        b.0.25 N.sub.0.75) 10.0 0.17 10   4/10                      7     550  1300 18 (Ti.sub.0.86 Ta.sub.0.04 W.sub.0.02 Mo.sub.0.08)--(C.su                        b.0.30 N.sub.0.70) 15.0 0.20 10   6/10                      Compari-                                                                       son blade                                                                      members                                                                        1     550   1320*                                                                              18 (Ti.sub.0.87 Ta.sub.0.04 W.sub.0.02 Mo.sub.0.07)--(C.su                        b.0.41 N.sub.0.59) 17.0*                                                                               0.28 10   10/10                     2     550   1310*                                                                              10 (Ti.sub.0.87 Ta.sub.0.04 W.sub.0.02 Mo.sub.0.07)--(C.su                        b.0.36 N.sub.0.64) 10.0 0.23 10   8/10                      3          --                              0.37 50   10/10                                                                Plastic deformation                                                            developed                           4          --                              0.31 100  4/10                                                                 Plastic deformation                                                            developed                           __________________________________________________________________________      *not falling within the range of this invention                          

As seen from Table 1, the blade members 1 to 7 of this invention exhibited excellent toughness, excellent wear resistance and excellent thermoplastic deformation resistance. On the other hand, the comparison blade members 1 to 4 were extremely inferior in such properties.

EXAMPLE 2

Powder materials described in Example 1 and powders of NbC (1.0 μm), ZrC (1.5 μm), Mo₂ C (1.2 μm) and TaN (1.0 μm) were selectively used as starting powder materials. The powder materials were mixed together in ratios shown in Table 2 to provide various mixtures. Each mixture was pressed into a densified solid body having a shape conforming to JIS·SNMG 432. Then, the densified solid bodies were sintered at temperature of 1450° C. for 1.5 hours under vacuum shown in Table 2 to form cermet substrates 8a to 14a of this invention and comparative cermet substrates 5a to 8a. The cermet substrates were substantially identical in composition to their respective mixtures. Then, the cermet substrates 8a to 14a of this invention were subjected to heat treatment under conditions shown in Table 3 to produce blade members 8 to 14 of this invention. Also, the comparison substrates 5a to 8a were subjected to heat treatment to produce comparison blade members 5 to 8. The substrates were subjected to the heat treatment in the above sintering furnace. Each comparison substrate had component contents not falling within this invention as indicated by mark * in Table 2. The comparison blade members 5 and 6 had free carbon in their reaction layer and at portions immediately adjacent thereto. The comparison blade member 7 had an extremely roughened surface.

The blade members 8 to 14 of this invention and the comparison blade members 5 to 8 were subjected to a continuous cutting test. The conditions for this continuous cutting test were as follows:

Workpiece: a bar of steel (JIS·SNCM-8; Hardness: HB240)

Cutting speed: 200 m/minute

Feed rate: 0.36 mm/revolution

Depth of cut: 1.5 mm

Time: 10 minutes

An intermittent cutting test was also carried out under the following cutting conditions:

Workpiece: a block of steel (JIS·SNCM-8; Hardness: HB280)

Cutting speed: 120 m/minute

Feed rate: 0.3 mm/revolution

Depth of cut: 2 mm

Time: 3 minutes

The results of the continuous and intermittent cutting tests are shown in Table 3.

                                      TABLE 2                                      __________________________________________________________________________              Composition (volume %)                                                 Kind of blade member                                                                    Hard phase constituting components TiCTiNTaCNbCZrCWCMo.sub.2                  CTaN                     Binder components MoNiCo                                                               ##STR1##                                                                             Sintering vacuum (torr)        __________________________________________________________________________     Substrates of this                                                             substrates                                                                      8a      50 13 -- -- --  5 --  -- 20 4 8 0.21   10.sup.-2                       9a      49 22 -- -- --  5 --  -- 12 4 8 0.31                                  10a      42 29 -- -- --  5 --  -- 12 4 8 0.41                                  11a      35 36 -- -- --  5 12  -- -- 4 8 0.51   10.sup.-1                      12a      29 42 -- -- --  5 12  -- -- 4 8 0.59                                  13a      31 20 10  5 -- 10 12  -- -- 4 8 0.39                                  14a      41 27 -- --  1  5 --   2 12 4 8 0.40   10.sup.-2                      Comparison                                                                     substrate                                                                       8a      71*                                                                               --*                                                                               -- -- --  5 --  -- 12 4 8 0*                                     6a      61*                                                                               10*                                                                               -- -- --  5 --  -- 12 4 8  0.14*                                 7a      24*                                                                               47*                                                                               -- -- --  5 12  -- -- 4 8  0.66* 10.sup.-1                       8a      70 18 --*                                                                               --*                                                                               --*                                                                               --*                                                                               --* --*                                                                               -- 4 8 0.20   10.sup.-2                      __________________________________________________________________________      *not falling within this invention                                       

                                      TABLE 3                                      __________________________________________________________________________                                                  Continuous                                                                             Intermittent              Heat treatment                               cutting cutting test                         Heat    Reaction layer            test    Number of chipped         Kind of                                                                              Pressure                                                                            tempera-                                                                               Composition of carbo-nitride metals:                                                                Average                                                                             Flank                                                                              Crater                                                                             blade members/            blade of N.sub.2                                                                          ture Time                                                                              (Ti, M) (CxNy)       thickness                                                                           wear                                                                               wear                                                                               number of tested          member                                                                               (torr)                                                                              (°C.)                                                                        (h)                                                                               (molar ratio)        (μm)                                                                             (mm)                                                                               (μm)                                                                            members                   __________________________________________________________________________     Blade                                                                          members of                                                                     this                                                                           invention                                                                       8    500  1280 6  (Ti.sub.0.77 W.sub.0.04 Mo.sub.0.19)--(C.sub.0.23                              N.sub.0.77)          4.0  0.17                                                                               20  3/10                       9                 (Ti.sub.0.84 W.sub.0.03 Mo.sub.0.13)--(C.sub.0.20                              N.sub.0.80)          4.5  0.15                                                                               15  3/10                      10                 (Ti.sub.0.86 W.sub.0.03 Mo.sub.0.11)--(C.sub.0.15                              N.sub.0.85)          4.5  0.13                                                                               15  2/10                      11    300          (Ti.sub.0.88 W.sub.0.03 Mo.sub.0.09)--(C.sub.0.12                              N.sub.0.88)          4.5  0.15                                                                               15  2/10                      12                 (Ti.sub.0.89 W.sub.0.03 Mo.sub. 0.08)--(C.sub.0.08                             N.sub.0.92)          4.5  0.20                                                                               10  4/10                      13    500          (Ti.sub.0.65 Ta.sub.0.14 Nb.sub.0.06 W.sub.0.07                                Mo.sub.0.08)--(C.sub.0.19 N.sub.0.81)                                                               4.0  0.19                                                                               25  1/10                      14                 (Ti.sub.0.83 Ta.sub.0.04 W.sub.0.03 Mo.sub.0.10)--(C.su                        b.0.18 N.sub.0.82)   4.5  0.17                                                                               20  2/10                      Compari-                                                                       son blade                                                                      member                                                                          5                 (Ti.sub.0.83 W.sub.0.03 Mo.sub.0.14)--(C.sub.0.56                              N.sub.0.44)          3.5  0.35                                                                               50  10/10                      6                 (Ti.sub.0.84 W.sub.0.03 Mo.sub.0.13)--(C.sub.0.30                              N.sub.0.70)          4.0  0.30                                                                               30  7/10                       7    300          (Ti.sub.0.89 W.sub.0.03 Mo.sub.0.08)--(C.sub.0.05                              N.sub.0.95)          4.5  0.37                                                                               20  9/10                       8    500          Ti--(C.sub.0.22 N.sub.0.78)                                                                         4.5  0.30                                                                               25  10/10                     __________________________________________________________________________

As can be seen from Table 3, the blade members 8 to 14 of this invention exhibited excellent wear resistance and excellent toughness and achieved an excellent cutting performance. On the other hand, the comparison blade members 5 to 8, whose substrates had the compositions not falling within the range of this invention, were very inferior in wear resistance and toughness and exhibited a poor cutting performance.

EXAMPLE 3

Cermet substrates, composed of 26.5% by volume TiC, 20% TiN, 10% TaC, 15% WC, 10% Mo, 5.5% Ni, 11% Co and 2% Al (the volume ratio of TiN to TiC plus TiN: 0.43), were prepared according to the procedure of Example 1. The cermet substrates were subjected to heat treatment under conditions shown in Table 4 to produce blade members 15 to 19 of this invention and comparison blade member 9. The cermet substrate not subjected to heat treatment was used as comparison blade member 10. Also, there were provided WC-based comparison blade member 11 (JIS·P10) and comparison WC-based blade member 12 having on a surface 7 μm thick coating composed of TiC layer and TiN layer.

The blade members 15 to 19 of this invention and the comparison blade members 9 to 12 were subjected to a continuous cutting test. The conditions for this continuous cutting test were as follows:

Workpiece: a bar of steel (JIS·SNCM-8; Hardness: HB240)

Cutting speed: 160 m/minute

Feed rate: 0.44 mm/revolution

Depth of cut: 1.5 mm

Time: 15 minutes

An intermittent cutting test was also carried out under the following cutting conditions:

Workpiece: a block of steel (JIS·SNCM-8; Hardness: HB280)

Cutting speed: 100 m/minute

Feed rate: 0.335 mm/revolution

Depth of cut: 2 mm

Time: 3 minutes

The results of the continuous and intermittent cutting tests are shown in Table 4.

                                      TABLE 4                                      __________________________________________________________________________                                                   Continuous                                                                             Intermittent                                                                   cutting test                      Heat treatment                       cutting Number                                 Heat    Reaction layer          test   of chipped                         Pressure                                                                            tempera-                                                                               Composition of carbo-nitride metals:                                                              Average                                                                             Flank                                                                              Crater                                                                            blade members/            Kind of  of N.sub.2                                                                          ture Time                                                                              (Ti, M) (CxNy)     thickness                                                                           wear                                                                               wear                                                                              number of tested          blade member                                                                            (torr)                                                                              (°C.)                                                                        (h)                                                                               (molar ratio)      (μm)                                                                             (mm)                                                                               (μm)                                                                           members                   __________________________________________________________________________     Blade members of                                                               this invention                                                                 15       200  1100 16 Not measurable     0.5  0.30                                                                               50 1/10                      16            1150    (Ti.sub.0.67 Ta.sub.0.13 W.sub.0.09 Mo.sub.0.11)--(C                           .sub.0.30 N.sub.0.70)                                                                             1.0  0.21                                                                               40 1/10                      17       300  1200 10 (Ti.sub.0.68 Ta.sub.0.13 W.sub.0.09 Mo.sub.0.10)--(C                           .sub.0.25 N.sub.0.75)                                                                             2.0  0.19                                                                               30 1/10                      18       400  1260  6 (Ti.sub.0.72 Ta.sub.0.12 W.sub.0.07 Mo.sub.0.09)--(C                           .sub. 0.15 N.sub.0.85)                                                                            3.0  0.16                                                                               20 1/10                      19       500  1280  7 (Ti.sub.0.72 Ta.sub.0.12 W.sub.0.07 Mo.sub.0.09)--(C                           .sub.0.16 N.sub.0.84)                                                                             4.0  0.15                                                                               20 2/10                      Comparison                                                                     blade members                                                                   9       200   1050*                                                                              16 Not measurable      0.3*                                                                               0.39                                                                               65 1/10                      10       --                              --   0.47                                                                               80 2/10                      11       --                                   0.53                                                                               150                                                                               4/10                      12       --                                   0.35                                                                               60 3/10                      __________________________________________________________________________      *not falling within the range of this invention                          

As can be seen from Table 4, the blade members 15 to 19 of this invention exhibited excellent wear resistance and excellent toughness in comparison with the comparison blade members 11 and 12. The reaction layer of the comparison blade member 9 had an average thickness of 0.3 μm which is below the lower limit of the thickness range of this invention. The comparison blade member 10 had no reaction surface layer. Therefore, the two comparison blade members 9 and 10 were substantially equal in toughness to the blade members of this invention but were inferior in wear resistance.

The following Examples 4 to 6 illustrate blade members having on a surface a reaction layer composed of oxy-carbo-nitride of metals.

EXAMPLE 4

Cermet substrates were prepared according to the procedure of Example 1 using the same powder materials, the cermet substrates having the same composition as the cermet substrates of Example 1. The cermet substrates were then ground into a shape conforming to JIS·SNP432. The cermet substrates were then subjected to heat treatment in an atmosphere of CO₂ or in an atmosphere of CO₂ and N₂ under conditions shown in Table 5 to produce blade members 20 to 26 of this invention and comparison blade members 13 and 14. The comparison blade members 13 and 14 were produced under the conditions not falling within the range of this invention, as shown in Table 5. Also, there were provided comparison blade member 15 of cermet containing TiC, Ni and Mo and WC-based comparison blade member 16 having on a surface 6 μm thick coating composed of a layer of TiC and a layer of Al₂ O₃.

The blade members 20 to 26 of this invention and the comparison blade members 13 to 16 were subjected to a continuous cutting test and an intermittent cutting test. The conditions for this continuous cutting test were as follows:

Workpiece: a bar of steel (JIS·SNCM-8; Hardness: HB220)

Cutting speed: 250 m/minute

Feed rate: 0.36 mm/revolution

Depth of cut: 1.5 mm

Time: 10 minutes

The conditions for the intermittent cutting test were as follows:

Workpiece: a block of steel (JIS·SNCM-8; Hardness: HB280)

Cutting speed: 140 m/minute

Feed rate: 0.3 mm/revolution

Depth of cut: 2 mm

Time: 3 minutes

The results of these two continuous and intermittent cutting tests are shown in Table 5.

                                      TABLE 5                                      __________________________________________________________________________                                                               Inter-                                                                         mittent                                                                        cutting                                                                        test                                                                           Number                                                                         of                                                                             chipped                                                                        blade                                                                          mem-                 Heat treatment                                  Continuous                                                                               bers/ng              Pres-     Pres-                                                                              Heat    Reaction layer            test      number               Kind of                                                                              sure                                                                               sure                                                                               tempera-                                                                               Composition of oxy-carbo-nitride of                                                                 Average                                                                             Flank                                                                               Crater                                                                              of tested            blade of CO.sub.2                                                                        of N.sub.2                                                                         ture Time                                                                              metals: (Ti, M) (CxNyOz)                                                                            thickness                                                                           wear wear blade                member                                                                               (torr)                                                                             (torr)                                                                             (°C.)                                                                        (h)                                                                               (molar ratio)        (μm)                                                                             (mm) (μm)                                                                             members              __________________________________________________________________________     Blade                                                                          members of                                                                     this                                                                           invention                                                                      20    350 --  1250 12 (Ti.sub.0.81 Ta.sub.0.06 W.sub.0.03 Mo.sub.0.10)--(C                           .sub.0.60 N.sub.0.20 O.sub.0.20)                                                                    1.5  0.18 25   1/10                 21    300 --  1260 10 (Ti.sub.0.81 Ta.sub.0.06 W.sub.0.03 Mo.sub.0.10)--(C                           .sub.0.60 N.sub.0.20 O.sub.0.20)                                                                    2.0  0.16 20   2/10                 22    250 --  1270  8 (Ti.sub.0.82 Ta.sub.0.05 W.sub.0.03 Mo.sub.0.10)--(C                           .sub.0.58 N.sub.0.20 O.sub.0.22)                                                                    2.0  0.15 20   2/10                 23    200 --  1280  6 (Ti.sub.0.82 Ta.sub.0.05 W.sub.0.03 Mo.sub.0.10)--(C                           .sub.0.55 N.sub.0.20 O.sub.0.25)                                                                    2.0  0.15 20   2/10                 24    100 200 1280  8 (Ti.sub.0.83 Ta.sub.0.05 W.sub.0.03 Mo.sub.0.09)--(C                           .sub.0.30 N.sub.0.55 O.sub.0.15)                                                                    4.5  0.13 15   3/10                 25    100 300 1290 15 (Ti.sub.0.85 Ta.sub.0.04 W.sub.0.03 Mo.sub.0.08)--(C                           .sub.0.17 N.sub.0.65 O.sub.0.18)                                                                    7.5  0.15 10   4/10                 26    150 400 1300 20 (Ti.sub.0.87 Ta.sub.0.04 W.sub.0.02 Mo.sub.0.07)--(C                           .sub.0.10 N.sub.0.70 O.sub.0.20)                                                                    10.0 0.16 10   5/10                 Compari-                                                                       son blade                                                                      members                                                                        13    150 400  1320*                                                                              20 (Ti.sub.0.88 Ta.sub.0.04 W.sub.0.02 Mo.sub.0.06)--(C                           .sub.0.05 N.sub.0.75 O.sub.0.20)                                                                    12.0*                                                                               0.20 10   10/10                14    --* --* 1280  6 --                   --   0.42 50   2/10                                                                 Plastic Deformation            15    --                                        0.39 55   10/10                                                                Plastic Deformation            16    --                                        0.36 100  4/10                                                                 Plastic                        __________________________________________________________________________                                                     Deformation                     *not falling within this invention                                       

As can be seen from Table 5, the blade members 20 to 26 exhibited excellent toughness, excellent wear resistance and excellent thermoplastic deformation resistance. The comparison blade members 15 and 16 were extremely inferior in these properties. The comparison blade member 13 was extremely inferior in toughness, and the comparison blade member 14 were extremely inferior in wear resistance and thermoplastic deformation resistance.

EXAMPLE 5

The same powder materials described in Example 2 were mixed together in ratios shown in Table 2 to provide various mixtures. Cermet substrates 8a to 14a and comparison substrates 5a to 8a were produced from these mixtures according to the same procedure of Example 2. The cermet substrates 8a to 14a of this invention were subjected to heat treatment under conditions shown in Table 6 to produce blade members 27 to 33 of this invention, respectively. Also, the comparison cermet substrates 5a to 8a were subjected to heat treatment under conditions shown in Table 6 to produce comparison blade members 17 to 20, respectively. The comparison blade members 17 and 18 had free carbon in their reaction layers and at portions immediately adjacent thereto. The comparison blade member 19 had an extremely roughened surface.

The blade members 27 to 33 of this invention and the comparison blade members 17 to 20 were subjected to a continuous cutting test and an intermittent cutting test.

The conditions for this continuous cutting test were as follows:

Workpiece: a bar of steel (JIS·SNCM-8; Hardness: HB260)

Cutting speed: 200 m/minute

Feed rate: 0.36 mm/revolution

Depth of cut: 1.5 mm

Time: 10 minutes

The conditions for the intermittent cutting test were as follows:

Workpiece: a block of steel (JIS·SNCM-8; Hardness: HB280)

Cutting speed: 120 m/minute

Feed rate: 0.3 mm

Depth of cut: 2 mm

Time: 3 minutes

The results of the continuous and intermittent cutting tests are shown in Table 6.

                                      TABLE 6                                      __________________________________________________________________________                                                               Inter-                                                                         mittent                                                                        cutting                                                                        test                                                                           Number                                                                         of                                                                             chipped              Heat treatment                                  Continuous                                                                               bladeng              Pres-     Pres-                                                                              Heat    Reaction layer            test      mem-                 Kind of                                                                              sure                                                                               sure                                                                               tempera-                                                                               Composition of oxy-carbo-nitride of                                                                 Average                                                                             Flank                                                                               Crater                                                                              bers/                blade of CO.sub.2                                                                        of N.sub.2                                                                         ture Time                                                                              metals: (Ti, M) (CxNyOz)                                                                            thickness                                                                           wear wear tested               member                                                                               (torr)                                                                             (torr)                                                                             (°C.)                                                                        (h)                                                                               (molar ratio)        (μm)                                                                             (mm) (μm)                                                                             members              __________________________________________________________________________     Blade                                                                          members of                                                                     this                                                                           invention                                                                      27    200 --  1280 7  (Ti.sub.0.77 W.sub.0.04 Mo.sub.0.18)--(C.sub.0.62                              N.sub.0.13 O.sub.0.25)                                                                              1.5  0.16 25   3/10                 28                    (Ti.sub.0.85 W.sub.0.03 Mo.sub.0.12)--(C.sub.0.58                              N.sub.0.17 O.sub.0.25)                                                                              2.0  0.14 20   2/10                 29                    (Ti.sub.0.86 W.sub.0.03 Mo.sub.0.11)-- (C.sub.0.53                             N.sub.0.22 O.sub.0.25)                                                                              2.0  0.13 15   1/10                 30    100 --          (Ti.sub.0.88 W.sub.0.03 Mo.sub.0.09)--(C.sub.0.48                              N.sub.0.27 O.sub.0.25)                                                                              2.0  0.15 15   2/10                 31                    (Ti.sub.0.89 W.sub.0.03 Mo.sub.0.08)--(C.sub.0.44                              N.sub.0.30 O.sub.0.26)                                                                              2.5  0.19 10   3/10                 32    100 200         (Ti.sub.0.66 Ta.sub.0.13 Nb.sub.0.06 W.sub.0.07                                Mo.sub.0.08)--       4.0  0.18 20   1/10                                       (C.sub.0.88 N.sub.0.60 O.sub.0.12)                       33    100 200         (Ti.sub.0.84 Ta.sub.0.03 W.sub.0.03 Mo.sub.0.10)--(C                           .sub.0.28 N.sub.0.55 O.sub.0.17)                                                                    4.0  0.16 15   2/10                 Compari-                                                                       son blade                                                                      members                                                                        17    200 --          (Ti.sub.0.85 W.sub.0.03 Mo.sub.0.12)--(C.sub.0.88                              O.sub.0.12)          0.8  0.33 50   10/10                18                    (Ti.sub.0.85 W.sub.0.03 Mo.sub.0.12)--(C.sub.0.71                              N.sub.0.09 O.sub.0.20)                                                                              1.0  0.29 35   6/10                 19    100 --          (Ti.sub.0.89 W.sub.0.03 Mo.sub.0.08)--(C.sub.0.37                              N.sub.0.33 O.sub.0.30)                                                                              2.5  0.37 15   9/10                 20    200 --          Ti--(C.sub.0.60 N.sub.0.12 O.sub.0.28)                                                              2.0  0.28 30   10/10                __________________________________________________________________________

As can be seen from Table 6, the blade members 27 to 33 of this invention exhibited excellent wear resistance and excellent toughness and achieved a good cutting performance. On the other hand, the comparison blade members 17 to 20 whose substrates had the compositions not falling within the range of this invention, were very inferior in wear resistance and toughness and exhibited a poor cutting performance.

EXAMPLE 6

Cermet substrates, composed of 26.5% by volume TiC, 20% TiN, 10% TaC, 15% WC, 10% Mo, 5.5% Ni, 11% Co and 2% Al (the volume ratio of TiN to TiC plus TiN: 0.43), were prepared according to the procedure of Example 1. The cermet substrates were subjected to heat treatment under conditions shown in Table 7 to produce blade members 34 to 38 of this invention and comparison blade member 21. The cermet substrate not subjected to heat treatment was used as comparison blade member 22. Also, there were provided WC-based comparison blade member 23 (JIS·P10) and comparison WC-based blade member 24 having on a surface 7 μm thick coating composed of TiC layer and TiN layer.

The blade members 34 to 38 of this invention and the comparison blade members 21 to 24 were subjected to a continuous cutting test. The conditions for this continuous cutting test were as follows:

Workpiece: a bar of steel (JIS·SNCM-8; Hardness: HB260)

Cutting speed: 150 m/minute

Feed rate: 0.44 mm/revolution

Depth of cut: 1.5 mm

Time: 15 minutes

An intermittent cutting test was also carried out under the following cutting conditions:

Workpiece: a block of steel (JIS·SNCM-8; Hardness: HB280)

Cutting speed: 100 m/minute

Feed rate: 0.335 mm/revolution

Depth of cut: 2 mm

Time: 5 minutes

The results of the continuous and intermittent cutting tests are shown in Table 7.

                                      TABLE 7                                      __________________________________________________________________________                                                               Inter-                                                                         mittent                                                                        cutting                                                                        test                                                                           Number                                                                         of                                                                             chipped              Heat treatment                                  Continuous                                                                               bladeng              Pres-     Pres-                                                                              Heat    Reaction layer            test      mem-                 Kind of                                                                              sure                                                                               sure                                                                               tempera-                                                                               Composition of oxy-carbo-nitride of                                                                 Average                                                                             Flank                                                                               Crater                                                                              bers/                blade of CO.sub.2                                                                        of N.sub.2                                                                         ture Time                                                                              metals (Ti, M) (CxNyOz)                                                                             thickness                                                                           wear wear tested               member                                                                               (torr)                                                                             (torr)                                                                             (°C.)                                                                        (h)                                                                               (molar ratio)        (μm)                                                                             (mm) (μm)                                                                             members              __________________________________________________________________________     Blade                                                                          members of                                                                     this                                                                           invention                                                                      34    100 --  1100    Not measurable       0.5  0.25 40   1/10                 35            1150 20 Not measurable       0.8  0.18 30   1/10                 36        200 1200    (Ti.sub.0.69 Ta.sub.0.13 W.sub.0.08 Mo.sub.0.10)--(C                           .sub.0.50 N.sub.0.45 O.sub.0.05)                                                                    2.0  0.16 15   1/10                 37    200 --  1280 6  (Ti.sub.0.72 Ta.sub.0.12 W.sub.0.07 Mo.sub.0.09)--(C                           .sub.0.65 N.sub.0.25 O.sub.0.10 )                                                                   1.5  0.13 10   1/10                 38    100 200         (Ti.sub.0.73 Ta.sub.0.12 W.sub.0.06 Mo.sub.0.09)--(C                           .sub.0.25 N.sub.0.60 O.sub.0.15)                                                                    3.5  0.13 10   1/10                 Compari-                                                                       son blade                                                                      members                                                                        21        --   1050*                                                                              20 Not measurable       0.3* 0.34 50   1/10                 22    --                                   --   0.46 80   2/10                 23    --                                        0.52 150  5/10                 24    --                                        0.33 40   3/10                 __________________________________________________________________________      *not falling within the range of this invention                          

As can be seen from Table 7, the blade members 34 to 38 of this invention exhibited excellent wear resistance and excellent toughness in comparison with the comparison blade members 23 and 24. The reaction layer of the comparison blade member 21 had an average thickness of 0.3 μm which is below the lower limit of the thickness range of this invention. The comparison blade member 22 had no reaction layer. Therefore, the two comparison blade members 21 and 22 were substantially equal in toughness to the blade members of this invention but were inferior in wear resistance.

The following Examples 7 to 9 illustrate blade members having on a surface a reaction layer composed of an inner layer of carbo-nitride of metals and an outer layer of oxy-carbo-nitride of metals.

EXAMPLE 7

Cermet substrates were prepared according to the procedure of Example 1 using the same powder materials, the cermet substrates having the same composition as the cermet substrates of Example 1. The cermet substrates were then ground into a shape conforming to JIS·SNP432. The cermet substrates were then subjected to heat treatment in an atmosphere of N₂ under conditions shown in Table 8 to form a first reaction layer of carbo-nitride of metals on a surface thereof. Subsequently, the cermet substrates were subjected to heat treatment in an atmosphere of CO₂ under conditions shown in Table 8 to form an outer reaction layer of oxy-carbo-nitride of metals in the first reaction layer, thereby producing blade members 39 to 45 of this invention and comparison blade members 25 and 26. The comparison blade members 25 and 26 were produced under the conditions not falling within the range of this invention, as shown in Table 8. Also, there were provided comparison blade member 27 of cermet containing TiC, Ni and Mo and WC-based comparison blade member 28 having on a surface 6 μm thick coating composed of a layer of TiC and a layer of Al₂ O₃.

The blade members 39 to 45 of this invention and the comparison blade members 25 to 28 were subjected to a continuous cutting test and an intermittent cutting test for the same purposes in the above Examples.

The conditions for the continuous cutting test were as follows:

Workpiece: a bar of steel (JIS·SNCM-8; Hardness: HB240)

Cutting speed: 260 m/minute

Feed rate: 0.375 mm/revolution

Depth of cut: 2.0 mm

Time: 10 minutes

The conditions for the intermittent cutting test were as follows:

Workpiece: a block of steel (JIS·SNCM-8; Hardness: HB280)

Cutting speed: 150 m/minute

Feed rate: 0.33 mm/revolution

Depth of cut: 2.0 mm

Time: 3 minutes

The results obtained are shown in Table 8.

                                      TABLE 8                                      __________________________________________________________________________              Heat treatment                     Reaction layer                                                Outer layer      Inner layer                        Kind of  Inner layer             Heat tem-  Composition of                                                                               Averageitride        blade    Pressure of                                                                          Heat temp-  Pressure of                                                                          perature   of metals: (Ti, M)                                                                           thickness            member   N.sub.2 (torr)                                                                       erature (°C.)                                                                  Time (h)                                                                            CO.sub.2 (torr)                                                                      (°C.)                                                                         Time (h)                                                                            (molar ratio) (μm)              __________________________________________________________________________     Blade member of                                                                this invention                                                                 39       600   1240   8    300   1250  6    (Ti.sub.0.85 Ta.sub.0.05                                                       W.sub.0.03 Mo.sub.0.07)--                                                                    3.0                                                              (C.sub.0.18 N.sub.0.82)            40       550   1250   7    250   1260  5    (Ti.sub.0.85 Ta.sub.0.05                                                       W.sub.0.03 Mo.sub.0.07)--                                                                    3.5                                                              (C.sub.0.15 N.sub.0.85)            41       500   1260   6    200   1270  4    (Ti.sub.0.87 Ta.sub.0.05                                                       W.sub.0.03 Mo.sub.0.05)--                                                                    3.5                                                              (C.sub.0.15 N.sub.0.85)            42       450   1270   5    200   1280  3    (Ti.sub.0.87 Ta.sub.0.05                                                       W.sub.0.03 Mo.sub.0.05)--                                                                    3.5                                                              (C.sub.0.17 N.sub.0.83)            43       400   1280   7    250   1280  6    (Ti.sub.0.88 Ta.sub.0.04                                                       W.sub.0.03 Mo.sub.0.05)--                                                                    5.5                                                              (C.sub.0.20 N.sub.0.80)            44       450   1290   11   300   1290  7    (Ti.sub.0.90 Ta.sub.0.04                                                       W.sub.0.03 Mo.sub.0.03)--                                                                    8.0                                                              (C.sub.0.25 N.sub.0.75)            45       550   1300   12   300   1300  9    (Ti.sub.0.92 Ta.sub.0.03                                                       W.sub.0.02 Mo.sub.0.03)--                                                                    10.0                                                             (C.sub.0.30 N.sub.0.70)            Comparison blade                                                               members                                                                        25       550    1320* 15   300   1300  6    (Ti.sub.0.94 Ta.sub.0.02                                                       W.sub.0.02 Mo.sub.0.02)--                                                                    16.0                                                             (C.sub.0.41 N.sub.0.59)            26       550   1300   6    400    1330*                                                                               18   (Ti.sub.0.92 Ta.sub.0.03                                                       W.sub.0.02 Mo.sub.0.03)--                                                                    5.0                                                              (C.sub.0.35 N.sub.0.65)            27       --                                                                    28       --                                                                    __________________________________________________________________________                             Reaction layer                                                                 Outer layer                                                                    Composition of oxy-carbo-                                                                         Continuous cutting                                                                          Intermittent                                                                   cutting test                          Kind of  nitride of metals: (Ti, M)                                                                   Average                                                                             test         Number of                             blade    (CxNyOz)      thickness                                                                           Flank wear                                                                           Crater                                                                                chipped blade                                                                  members/                              member   (molar ratio) (μm)                                                                             (mm)  (μm)                                                                               number of tested                                                               members                __________________________________________________________________________                    Blade member of                                                                this invention                                                                 39       (Ti.sub.0.90 Ta.sub.0.04 W.sub.0.02 Mo.sub.0.04)--                                           0.7  0.13  20     0/10                                           (C.sub.0.35 N.sub.0.53 O.sub.0.12)                                    40       (Ti.sub.0.90 Ta.sub.0.04 W.sub.0.02 Mo.sub.0.04)--                                           1.0  0.11  15     1/10                                           (C.sub.0.35 N.sub.0.50 O.sub.0.15)                                    41       (Ti.sub.0.92 Ta.sub.0.03 W.sub.0.02 Mo.sub.0.03)--                                           1.0  0.10  15     1/10                                           (C.sub.0.35 N.sub.0.50 O.sub.0.15)                                    42       (Ti.sub.0.92 Ta.sub.0.03 W.sub.0.02 Mo.sub.0.03)--                                           1.0  0.09  15     1/10                                           (C.sub.0.40 N.sub.0.43 O.sub.0.17)                                    43       (Ti.sub.0.92 Ta.sub.0.03 W.sub.0.02 Mo.sub.0.03)--                                           2.0  0.09  10     2/10                                           (C.sub.0.43 N.sub.0.40 O.sub.0.17)                                    44       (Ti.sub.0.95 Ta.sub.0.02 W.sub.0.01 Mo.sub.0.02)--                                           3.5  0.13   5     3/10                                           (C.sub.0.45 N.sub.0.35 O.sub.0.20)                                    45       (Ti.sub.0.95 Ta.sub.0.02 W.sub.0.01 Mo.sub.0.02)--                                           4.5  0.15   5     5/10                                           (C.sub.0.48 N.sub.0.30 O.sub.0.22)                                    Comparison blade                                                               members                                                                        25       (Ti.sub.0.97 Ta.sub.0.01 Mo.sub.0.02)--                                                      3.0  0.26   5     10/10                                          (C.sub.0.55 N.sub.0.23 O.sub.0.22)                                    26       (Ti.sub.0.95 Ta.sub.0.02 W.sub.0.01 Mo.sub.0.02)--                                           11.0*                                                                               0.22   5     10/10                                          (C.sub.0.50 N.sub.0.25 O.sub.0.25)                                    27       --                 0.42  70     10/10                                                             Plastic                                                                        deformation                                        28       --                 0.39  120    5/10                                                              Plastic                                                                        deformation                         __________________________________________________________________________      *not falling within this invention                                       

As can be seen from Table 8, the blade members 39 to 45 of this invention were much superior to the comparison blade members 27 and 28 in wear resistance, thermoplastic deformation resistance and toughness. The comparison blade member 25 had 16.0 μm thick inner layer which exceeded the upper limit of the thickness range of this invention. The comparison blade member 26 had 11.0 μm thick outer layer which exceeded the upper limit of the thickness range of this invention. These comparison blade members 25 and 26 were much inferior in toughness.

EXAMPLE 8

The same powder materials described in Example 2 were mixed together in ratios shown in Table 6 to provide various mixtures. Cermet substrates 8a to 14a and comparison substrates 5a to 8a were produced from these mixtures according to the same procedure of Example 2. Then, the cermet substrates 8a to 14a of this invention were subjected to heat treatment under conditions shown in Table 9 to produce blade members 46 to 52 of this invention, respectively. Also, the comparison substrates 5a to 8a were subjected to heat treatment under conditions shown in Table 9 to produce comparison blade members 29 to 32, respectively. The comparison blade members 29 and 30 had free carbon in their reaction layers and at portions immediately adjacent thereto. The comparison blade member 31 had an extremely roughened surface.

The blade members 46 to 52 of this invention and the comparison blade members 29 to 32 were subjected to a continuous cutting test. The conditions for this continuous cutting test were as follows:

Workpiece: a bar of steel (JIS·SNCM-8; Hardness: HB240)

Cutting speed: 210 m/minute

Feed rate: 0.36 mm/revolution

Depth of cut: 2.0 mm

Time: 10 minutes

An intermittent cutting test was also carried out under the following conditions:

Workpiece: a block of steel (JIS·SNCM-8; Hardness: HB280)

Cutting speed: 130 m/minute

Feed rate: 0.3 mm/revolution

Depth of cut: 2.0 mm

Time: 3 minutes

The results of these two tests are shown in Table 9.

                                      TABLE 9                                      __________________________________________________________________________     Heat treatment                            Reaction layer                                            Outer layer          Inner layer                          Kind of                                                                              Inner layer                Heat tem-                                                                               Composition of                                                                                 Averageitride        blade Pressure of                                                                          Heat temp-                                                                           Time                                                                              Pressure of                                                                          Pressure of                                                                          perature                                                                             Time                                                                              of metals: (Ti, M)                                                                             thickness            member                                                                               N.sub.2 (torr)                                                                       erature (°C.)                                                                 (h)                                                                               CO.sub.2 (torr)                                                                      CO (torr)                                                                            (°C.)                                                                         (h)                                                                               (molar ratio)   (μm)              __________________________________________________________________________     Blade                                                                          members of                                                                     this                                                                           invention                                                                      46    500   1280  5        200   1280  3  (Ti.sub.0.82 W.sub.0.04                                                        Mo.sub.0.14)--  3.5                                                            (C.sub.0.20 N.sub.0.80)              47                                        (Ti.sub.0.89 W.sub.0.03                                                        Mo.sub.0.08)--  4.0                                                            (C.sub.0.18 N.sub.0.82)              48                   --                   (Ti.sub.0.91 W.sub.0.03                                                        Mo.sub.0.06)--  4.0                                                            (C.sub.0.15 N.sub.0.85)              49    300                  100            (Ti.sub.0.92 W.sub.0.03                                                        Mo.sub.0.05 )-- 4.0                                                            (C.sub.0.12 N.sub.0.88)              50                                        (Ti.sub.0.94 W.sub.0.02                                                        Mo.sub.0.04)--  4.0                                                            (C.sub.0.08 N.sub.0.92)              51    500            100                  (Ti.sub.0.81 Ta.sub.0.07                                                       Nb.sub.0.02 W.sub.0.05 Mo.sub.0.                                               05)--           3.5                                                            (C.sub.0.16 N.sub.0.84)              52                                        (Ti.sub.0.90 Ta.sub.0.02                                                       W.sub.0.03 Mo.sub.0.05)--                                                                      4.0                                                            (C.sub.0.16 N.sub.0.84)              Compari-                                                                       son blade                                                                      members                                                                        29                         200            (Ti.sub.0.87 W.sub.0.03                                                        Mo.sub.0.10)--  3.0                                                            (C.sub.0.56 N.sub.0.44)              30                   --                   (Ti.sub.0.89 W.sub.0.03                                                        Mo.sub.0.08)--  3.5                                                            (C.sub.0.30 N.sub.0.70)              31    300                  100            (Ti.sub.0.95 W.sub.0.02                                                        Mo.sub.0.30)--  4.0                                                            (C.sub.0.05 N.sub.0.95)              32    500                  200            Ti--(C.sub.0.20 N.sub.0.80)                                                                    4.0                  __________________________________________________________________________                                                             Intermittent                                                                   Cutting test                                    Reaction layer                 Number of                                       Outer layer       Continuous   Chipped blade                                   Composition of oxy-carbo-                                                                        cutting      members/                                  Kind of                                                                              nitride of metals: (Ti, M)                                                                  Average                                                                             test         number of                                 blade (CxNyOz)     thickness                                                                           Flank wear                                                                           Craft wear                                                                            tested                                    member                                                                               (molar ratio)                                                                               (μm)                                                                             (mm)  (μm)                                                                               members                __________________________________________________________________________                        Blade                                                                          members of                                                                     this                                                                           invention                                                                      46    (Ti.sub.0.93 W.sub.0.02 Mo.sub.0.05)--                                                      1.0  0.11  15     3/10                                            (C.sub.0.40 N.sub.0.45 O.sub.0.15)                                       47    (Ti.sub.0.94 W.sub.0.02 Mo.sub.0.04)--                                                      1.0  0.10  10     2/10                                            (C.sub.0.40 N.sub.0.45 O.sub.0.15)                                       48    (Ti.sub.0.94 W.sub.0.02 Mo.sub.0.04)--                                                      1.0  0.09  10     1/10                                            (C.sub.0.38 N.sub.0.45 O.sub.0.17)                                       49    (Ti.sub.0.95 W.sub.0.02 Mo.sub.0.03)--                                                      1.0  0.10  10     2/10                                            (C.sub.0.33 N.sub.0.50 O.sub.0.17)                                       50    (Ti.sub.0.97 W.sub.0.01 Mo.sub.0.02)--                                                      1.0  0.15  10     3/10                                            (C.sub.0.25 N.sub.0.55 O.sub.0.20)                                       51    (Ti.sub.0.92 Ta.sub.0.03 Nb.sub.0.01 W.sub.0.02                                             1.0  0.13  15     1/10                                            Mo.sub.0.02) (C.sub.0.38 N.sub.0.45 O.sub.0.17)                          52    (Ti.sub.0.96 Ta.sub.0.01 W.sub.0.01 Mo.sub.0.02)                                            1.0  0.11  15     1/10                                            (C.sub.0.38 N.sub.0.45 O.sub.0.17)                                       Compari-                                                                       son blade                                                                      members                                                                        29    (Ti.sub.0.94 W.sub.0.01 Mo.sub.0.05)--                                                      1.0  0.30  40     10/10                                           (C.sub.0.60 N.sub.0.33 O.sub.0.07)                                       30    (Ti.sub.0.95 W.sub.0.01 Mo.sub.0.04)--                                                      1.0  0.28  30     7/10                                            (C.sub.0.45 N.sub.0.45 O.sub.0.10)                                       31    (Ti.sub.0.98 W.sub.0.01 Mo.sub.0.01)--                                                      1.0  0.35  15     9/10                                            (C.sub.0.25 N.sub.0.50 O.sub.0.25)                                       32    Ti--(C.sub.0.40 N.sub.0.45 O.sub.0.15)                                                      1.0  0.25  30     10/10                  __________________________________________________________________________

As can be seen from Table 9, the blade members 46 to 52 exhibited excellent wear resistance and excellent toughness and achieved a good cutting performance. On the other hand, the comparison blade members 29 to 32 whose substrates had the compositions not falling within the range of this invention, were very inferior in wear resistance toughness and exhibited a poor cutting performance.

EXAMPLE 9

Cermet substrates, composed of 26.5% by volume TiC, 20% TiN, 10% TaC, 15% WC, 10% Mo, 5.5% Ni, 11% Co and 2% Al (the volume ratio of TiN to TiC plus TiN: 0.43), were prepared according to the procedure of Example 1. The cermet substrates were subjected to heat treatment under conditions shown in Table 10 to produce blade members 53 to 57 of this invention and comparison blade members 33 to 36. The cermet substrate not subjected to the heat treatment was used as comparison blade member 36. Also, there were provided WC-based comparison blade member 37 (JIS·P10) and comparison WC-based blade member 38 having on a surface 7 μm thick coating composed of TiC layer and TiN layer.

The blade members 53 to 57 of this invention and the comparison blade members 33 to 38 were subjected to a continuous cutting test. The conditions for this continuous cutting test were as follows:

Workpiece: a bar of steel (JIS·SNCM-8; Hardness: HB240)

Cutting speed: 150 m/minute

Feed rate: 0.475 mm/revolution

Depth of cut: 2.0 mm

Time: 15 minutes

An intermittent cutting test was also carried out under the following cutting conditions:

Workpiece: a block of steel (JIS·SNCM-8; Hardness: HB280)

Cutting speed: 110 m/minute

Feed rate: 0.375 mm/revolution

Depth of cut: 2.0 mm

Time: 3 minutes

The results of the continuous and intermittent cutting tests are shown in Table 10.

                                      TABLE 10                                     __________________________________________________________________________            Heat treatment                      Reaction layer                                            Outer layer          Inner layer                         Kind of                                                                               Inner layer                Heat tem-                                                                               Composition of carbo-nitride                                                   of             Average              blade  Pressure of                                                                          Heat temp-                                                                           Time                                                                              Pressure of                                                                          Pressure of                                                                          perature                                                                             Time                                                                              metals: (Ti, M)                                                                               thickness            member N.sub.2 (torr)                                                                       erature (°C.)                                                                 (h)                                                                               CO.sub.2 (torr)                                                                      CO (torr)                                                                            (°C.)                                                                         (h)                                                                               (molar ratio)  (μm)              __________________________________________________________________________     Blade                                                                          members of                                                                     this invention                                                                 53     200   1100  10 --    100   1100  10 Not measurable 0.3                  54           1150                 1150     Not measurable 0.6                  55     300   1200  10             1200  10 (Ti.sub.0.82 Ta.sub.0.08                                                       W.sub.0.05 Mo.sub.0.05)--                                                                     2.0                                                             (C.sub.0.30 N.sub.0.70)             56     400   1260   5 100         1260   6 (Ti.sub.0.87 Ta.sub.0.06                                                       W.sub.0.04 Mo.sub.0.03)--                                                                     2.5                                                             (C.sub.0.16 N.sub.0.84)             57     500   1280   5             1280   4 (Ti.sub.0.88 Ta.sub.0.06                                                       W.sub.0.03 Mo.sub.0.03)                                                                       3.0                                                             (C.sub.0.15 N.sub.0.85)             Comparison                                                                     blade                                                                          members                                                                        33     200    1050*                                                                               12             --       Not measurable 0.2                  34     --             --    100   1050  10 --             --                   35     200   1050  10                      Not measurable  0.1*                36     --                                                                      37     --                                                                      38     --                                                                      __________________________________________________________________________                                                             Intermittent                                                                   cutting test                                    Reaction layer                 Number of                                       Outer layer       Continuous   chipped blade                                   Composition of oxy-carbo-                                                                        cutting      members/                                 Kind of                                                                               nitride of metals: (Ti, M)                                                                  Average                                                                             test         number of                                blade  (CxNyOz)     thickness                                                                           Flank wear                                                                           Crater                                                                                tested                                   member (molar ratio)                                                                               (μm)                                                                             (mm)  (μm)                                                                               members                __________________________________________________________________________                       Blade                                                                          members of                                                                     this invention                                                                 53     Not measurable                                                                              0.2  0.19  30     0/10                                     54     Not measurable                                                                              0.4  0.14  20     0/10                                     55     (Ti.sub.0.90 Ta.sub.0.04 W.sub.0.03 Mo.sub.0.03)-                              -            1.0  0.11  10     1/10                                            (C.sub.0.35 N.sub.0.55 O.sub.0.10)                                      56     (Ti.sub.0.92 Ta.sub.0.04 W.sub.0.02 Mo.sub.                                    0.02)--      1.0  0.10  10     1/10                                            (C.sub.0.35 N.sub.0.50 O.sub.0.15)                                      57     (Ti.sub.0.92 Ta.sub.0.04 W.sub.0.02 Mo.sub.0.02)-                              -            1.5  0.09   5     1/10                                            (C.sub.0.40 N.sub.0.43 O.sub.0.17)                                      Comparison                                                                     blade                                                                          members                                                                        33     --           --   0.40  70     0/10                                     34     Not measurable                                                                               0.1*                                                                               0.36  50     0/10                                     35     Not measurable                                                                               0.1*                                                                               0.29  45     0/10                                     36     --                0.48  80     1/10                                     37     --                0.57  170    5/10                                     38     --                0.40  80     3/10                   __________________________________________________________________________      *not falling within the range of this invention                          

As can be seen from Table 10, the blade members 53 to 57 of this invention exhibited excellent wear resistance and excellent toughness in comparison with the comparison blade members 37 and 38. The reaction layer of each of the comparison blade members 33 to 35 were below the lower limit of the thickness range of this invention. Further, the reaction layer of each of the comparison blade members 33 and 34 was a single layer. The comparison blade member 36 had no reaction layer. Although these comparison blade members 33 to 36 were substantially equal in toughness to the blade members of this invention, they were quite inferior in wear resistance. 

What is claimed is:
 1. A blade member for cutting tools which comprises a substrate of cermet containing, apart from impurities,10 to 35% by volume of at least one metal selected from the group consisting of Fe, Co, Ni, Cr, Mo, W and Al, 5 to 40% by volume of at least one compound selected from the group consisting of carbides and nitrides of metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, and balance titanium carbide and titanium nitride, in which the volume ratio of titanium nitride to titanium carbide plus titanium nitride is 0.2 to 0.6, said substrate having on a surface thereof a reaction layer composed of carbo-nitride of at least two metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, said at least two metals including Ti, said reaction layer having an average thickness of 0.5 to 15.0 μm, and the concentration of titanium in said reaction layer increases toward the surface thereof.
 2. A blade member for cutting tools which comprises a substrate of cermet containing, apart from impurities,10 to 35% by volume of at least one metal selected from the group consisting of Fe, Co, Ni, Cr, Mo, W and Al, 5 to 40% by volume of at least one compound selected from the group consisting of carbides and nitrides of metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, and balance titanium carbide and titanium nitride, in which the volume ratio of titanium nitride to titanium carbide plus titanium nitride is 0.2 to 0.6, said substrate having on a surface thereof a reaction layer composed of oxy-carbo-nitride of at least two metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, said at least two metals including Ti, said reaction layer having an average thickness of 0.5 to 15.0 μm, and the concentration of titanium in said reaction layer increases toward the surface thereof.
 3. A blade member for cutting tools which comprises a substrate of cermet containing, apart from impurities,10 to 35% by volume of at least one metal selected from the group consisting of Fe, Co, Ni, Cr, Mo, W and Al, 5 to 40% by volume of at least one compound selected from the group consisting of carbides and nitrides of metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, and balance titanium carbide and titanium nitride, in which the volume ratio of titanium nitride to titanium carbide plus titanium nitride is 0.2 to 0.6, said substrate having on a surface thereof a reaction layer consisting of inner and outer layers, said inner layer being composed of carbo-nitride of at least two metals, in groups IV_(A), V_(A) and VI_(A) of the periodic table, said at least two metals including Ti, and said inner layer having an average thickness of 0.2 to 15.0 μm, said outer layer being composed of oxy-carbo-nitride of at least two metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, said at least two metals including Ti, said outer layer having an average thickness of 0.2 to 10.0 μm, the combined average thickness of said inner and outer layers being 0.5 to 20.0 μm, and the concentration of titanium of each of said inner and outer layers of said reaction layer increases toward the surface thereof.
 4. A process for producing a blade member for cutting tools, which comprises the steps of:(a) mixing, apart from impurities, 10 to 35% by volume of at least one metal selected from the group consisting of Fe, Co, Ni, Cr, Mo, W and Al, 5 to 40% by volume of at least one compound selected from the group consisting of carbides and nitrides of metals in groups IV_(A), V_(A) and VI_(A) of periodic table, and balance titanium carbide and titanium nitride (the volume ratio of titanium nitride to titanium carbide plus titanium nitride is 0.2 to 0.6) to form a mixture, the above components being in the form of powder; (b) compacting the powder mixture into a densified solid body; (c) sintering the densified solid body under vacuum of not more than 10⁻¹ torr to form a substrate of cermet; and (d) heating the substrate in an atmosphere of nitrogen gas at temperatures of 1100° to 1300° C. so that a reaction layer is formed on a surface of the substrate, the reaction layer being composed of carbo-nitride of at least two metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, said at least two metals including Ti, and said reaction layer having an average thickness of 0.5˜15.0 μm.
 5. A process for producing a blade member for cutting tools, which comprises the steps of:(a) mixing, apart from impurities, 10 to 35% by volume of at least one metal selected from the group consisting of Fe, Co, Ni, Cr, Mo, W and Al, 5 to 40% by volume of at least one compound selected from the group consisting of carbides and nitrides of metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, and balance titanium carbide and titanium nitride (the volume ratio of titanium nitride to titanium carbide plus titanium nitride is 0.2 to 0.6) to form a mixture, the above components being in the form of powder; (b) compacting the powder mixture into a densified solid body; (c) sintering the densified solid body under vacuum of not more than 10⁻¹ torr to form a substrate of cermet; and (d) heating the substrate at temperatures of 1100° to 1300° C. in an atmosphere of at least one gas selected from the group consisting of CO and CO₂ so that a reaction layer is formed on a surface of the substrate, the reaction layer being composed of oxy-carbo-nitride of at least two metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, said at least two metals including Ti, and said reaction layer having an average thickness of 0.5˜10.0 μm.
 6. A process according to claim 5, in which said atmosphere further includes N₂.
 7. A process for producing a blade member for cutting tools, which comprises the steps of:(a) mixing, apart from impurities, 10 to 35% by volume of at least one metal selected from the group consisting of Fe, Co, Ni, Cr, Mo, W and Al, 5 to 40% by volume of at least one compound selected from the group consisting of carbides and nitrides of metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, and balance titanium carbide and titanium nitride (the volume ratio of titanium nitride to titanium carbide plus titanium nitride is 0.2 to 0.6) to form a mixture, the above components being in the form of powder; (b) compacting the powder mixture into a densified solid body; (c) sintering the densified solid body under vacuum of not more than 10⁻¹ torr to form a substrate of cermet; and (d) heating the substrate at temperatures of 1100° to 1300° C. in an atmosphere of N₂ so that a reaction layer is formed on a surface of the substrate, the reaction layer being composed of carbo-nitride of at least two metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, said at least two metals including Ti, and said reaction layer having an average thickness of 0.5˜20.0 μm. (e) subsequently heating the substrate at temperatures of 1100° to 1300° C. in an atmosphere of at least one gas selected from the group consisting of CO and CO₂ so that an outer reaction layer is formed in the surface of the reaction layer, said outer reaction layer being composed of oxy-carbo-nitride of at least two metals in groups IV_(A), V_(A) and VI_(A) of the periodic table, said at least two metals including Ti, said outer layer having an average thickness of 0.2 to 10.0 μm, and the inner portion of said reaction layer adjacent to said outer layer having an average thickness of 0.2 to 15.0 μm, and the combined average thicknesses of said inner portion and said outer layer being 0.5 to 20.0 μm. 